Oxygen and high-pressure air valves are used in many applications including oxygen tanks, SCUBA systems, filling stations, space capsules, in-home liquid oxygen tank systems, fuel pipe oxygen systems, aeroplane pilots' breathing apparatus, hospital breathing apparatus, steel, chemical and cold gasification plants, oxygen powered engines or any other associated processes. If oxygen is not properly controlled or used with equipment not specifically designed for oxygen, then accidents resulting in system failure and/or loss of plant, severe injury and death may occur.
Oxygen is an oxidising gas that vigorously supports burning. As a result, almost all materials are flammable and will burn actively at high temperatures in the presence of oxygen. Some materials which do not burn in air, will readily burn in oxygen-enriched atmospheres. In extreme cases, some materials may spontaneously burn in an oxygen-enriched environment if any heat generating mechanism is present and, if the concentration of this oxygen is sufficiently high, the burning of these materials may propagate to adjacent materials and devices.
Contaminants in oxygen systems are especially prone to ignite adjacent metallic and non-metallic materials and therefore greatly increase the potential for fire. When gas is compressed quickly inside a closed system such as a container or piping or a valve, the temperatures of the gas and adjacent materials can rise sharply. In an oxygen system, this rise in temperature can be high enough to cause ignition of contaminants such as oil, grease, solvents and materials such as dust, lint, metal chips, many organic and most non-metallic materials. Oxygen flowing at high speed through a valve or piping systems can also propel contaminants or particles with such force that friction or impact between the particles and/or system components can raise the temperature to ignition point of the contaminants, particles, or metallic system components, resulting in a major incident. It should also be appreciated that other ignition mechanisms are recognised to be present in these systems such as gas flow friction, mechanical friction, mechanical impact, electrical spikes and lightning strikes.
Ideally, cylinders, piping valves regulators, flame eaters and all other devices used in these systems will be constructed of non-flammable materials such as gold, silver (noble materials) and oxide ceramics. However, due to economic constraints and in order to achieve a non-leaking oxygen system, resilient sealing materials typically made of plastics, synthetic rubbers or some soft metals are often used. Unfortunately, these materials are less resistant to ignition than other metallic materials. Accordingly, materials with more favorable ignition and burning characteristics often result in leakages.